In the case of an operating error or failure of the transmission, emergency program shifting operations are carried out in order to change over the transmission to fail-safe state in which further travel with emergency running properties is possible.
Vehicles with high powered motorization and particularly shifting elements thereof become considerably loaded during an emergency shifting operation. The clutches concerned thus reach their load limits already after a few emergency program shifting operations under full load at high rotational speed of the engine, and this negatively affects the service life and accordingly the durability.
Constructional measures, such as enlargement of the clutch or increase of the number of discs for reducing the thermal load of the clutch that generates, are not adequate due to the installation space required.
An optimization of the lubrication or cooling or an increase in the amount of lubricant would not completely solve the problem. Besides, such a procedure would negatively affect the lubrication conditions in the rear-mounted unit of the transmission. In addition an extensive permanent testing would be needed on the test bench, which is associated with considerable expense and is time consuming.
For the above reasons, the use of thermally stabler clutch linings also is not the optimum solution.
The problem on which this invention is based is to indicate a method for load reduction of transmissions or clutches during emergency program shifting operations, which method can be economically and reliably applied without further mechanical constructional measures.